5-Heterocyclic-1,2,3,6-tetrahydro-4(5H)-pyrimidinethiones and pyrimidinone intermediates therefor

ABSTRACT

The compounds of this invention are 5-heterocyclic-1,2,3,6tetrahydro-4(5H)-pyrimidinethiones which have pharmacological activity, in particular gastric acid secretion inhibitory activity, and 5-heterocyclic-1,2,3,6-tetrahydro-4(5H)pyrimidinones which are intermediates in the preparation therefor.

United States Patent [1 1 3,910,914

Loev 5] Oct. 7, 1975 [54] S-HETEROCYCLIC-l,2,3,6-TETRAHYDRO- 3.225.040 12/1965 D'Amico et al 260/2565 R 4(5H)-PYRIMIDINETHIONES AND PYRIMIDINONE INTERMEDlATES Primary ExaminerD0nald G. Daus THEREFOR Assistant Examiner-James H. Turnipseed [75] Inventor: Bernard Loev, Broomall, Pa. Attorney, Agent, or FirmJanice E. Williams; Alan D. [73] Assignee: SmithKline Corporation, Loune; William Edgenon Philadelphia, Pa.

[22] Filed: Jan. 21, 1974 2| Appl. No.: 435,048

[5 7] ABSTRACT The compounds of this invention are S-heterocyclicl ,2,3,6-tetrahydro-4(SH )-pyrimidinethiones which [52] US. Cl..... 260/2565 R; 260/2564 C; 424/251 h l [51] Int. Cl. C07D 239/10 aye 'f 9 9 i y m particular l [58] Field of Search 260/256 5 R acid secretion inhibitory activity, and S-heterocyclucl,2,3,6-tctrahydr0-4(5H)-pyrimidinones which are in- [56] References cued termediates in the preparation therefor,

UNITED STATES PATENTS 3,l5l,l l4 9/1964 DAmico et al 260/2565 R 4 Claims, No Drawings S-HETEROCYCLIC- l ,2,3,6-TETRAHYDRO-4( SH PYRIMIDINETHIONES AND PYRIMIDINONE INTERMEDIATES THEREFOR This invention relates to new heterocyclic-l,2,3,6- tetrahydro-4( 5H )-pyrimidinethiones having pharmacological activity. In particular, these compounds inhibit gastric acid secretion. In addition, this invention relates to new S-hetcrocyclicl ,2,3 ,6-tetrahydro-4( 5H pyrimidinones which are useful as intermediates in the preparation of the corresponding pyrimidinethiones.

The pyrimidinethione compounds of this invention are represented by the following structural formula:

in which:

R, is Z-pyridyl, 2pyrimidinyl, 4-pyrimidinyl, 2- pyrazinyl. 2pyrrolyl, Z-quinolyl, 2-thiazolyl or 4- thiazolyl;

R is lower alkyl or phenyl optionally substituted with halogen, lower alkyl or lower alkoxy; and

R and R are hydrogen or lower alkyl or a pharmaceutically acceptable acid addition salt thereof.

The pharmacologically active compounds of this invention have the basic structure of formula I. However, it is apparent to one skilled in the art that well known nuclear substituents such as lower alkyl, lower alkoxy or halogen may be incorporated on the heterocyclic rings. These substituted compounds are used as are the parent compounds.

As used herein. the terms lower alkyl and lower alkoxy" denote groups having from one to four carbon atoms, straight or branched chain; halogen" denotes chloro, bromo or fluoro.

Preferred compounds of this invention are represented by formula I where R is Z-pyridyl. Advantageous compounds are represented by formula I where R is Z-pyridyl and R is phenyl optionally substituted with halogen, lower alkyl or lower alkoxy.

Particularly preferred is the compound l,2,3,6- tetrahydrol-methyl-5-phenyl'5-( Z-pyridyl )-4( 5H pyrimidine-thione.

The compounds of formula I produce inhibition of gastric acid secretion. In addition, they show antiarthritic and central nervous system depressant activity.

The inhibition of gastric acid secretion is demonstrated by administration of the compounds of formula I to pylorus ligated rats at doses of about lOO mg./kg. to about 200 mg./kg. orally. In this procedure, compounds which produce an increase in gastric pH or a decrease in the volume of gastric juice or both are considered active.

The compounds of formula I are prepared as shown below:

l 2 P r N where R R R and R are as defined above.

Thus, a Z-substituted-2-heterocyclic thioacetamide is reacted with ammonia or a primary amine and two molar equivalents of formaldehyde. The thioacetamide and/or the ammonia or primary amine may be used in the reaction procedure as the acid addition salt, for example as the hydrochloride or sulfate salt. The reaction may be carried out in aqueous solution but is preferably carried out in an alcoholic solution, for example in methanol or ethanol. The reaction is preferably run at about ambient temperature (ca. 25C.) to about C.

When R is hydrogen, the heterocyclic thioacetamidc starting materials (ll) are known to the art or are prepared, for example, by reacting the corresponding substituted acetonitrile (R,R CH-CN) with hydrogen sulfide in the presence of a base such as an amine or by reacting with ammonium polysulfide. The substituted aeetonitriles may be prepared from substituted ketones or carboxaldehydes (R R C==O) by reducing to the corresponding alcohol using a reducing agent such as sodium borohydride, then treating the alcohol with a chlorinating agent such as thionyl chloride and treating the resulting chloride with an alkali metal cyanide such as sodium or potassium cyanide.

When R is lower alkyl, the heterocyclic thioacetamides (ll) not known to the art are prepared by reacting a substituted methyl heterocycle (R R CH- with a base such as phenyl or butyl lithium and then with an appropriate isothiocyanate (R 'NCS where R is lower alkyl) to give the N-substituted 2-substituted-2- hcterocyelic thioacetamides. These compounds are also prepared by treatment of the corresponding heterocyclie thioamide where R. is hydrogen with an N-alkyl amine (R NH where R is lower alkyl).

Alternatively, the compounds of formula ll are prepared by treatment of the corresponding acetamides with phosphorus pentasulfide in a solvent such as benzene.

A further aspect of this invention is the 5 hetcroeyclicl ,2,3,6-tetrahydro-4( 5H)-pyrimidinones represented by the following structural formula:

N N R/ \R a 4 III in which:

R, is 2pyridyl, 2-pyrimidinyl. 4-pyrimidinyl, 2- pyrazinyl, Z-pyrrolyl, Z-quinolyl, 2-thiazolyl or 4- thiazolyl;

R is lower alkyl or phenyl optionally substituted with halogen, lower alkyl or lower alkoxy; and

R and R are hydrogen or lower alkyl or a pharmaceutically acceptable acid addition salt thereof.

Preferred and advantageous compounds of formula lll are those used in preparing the corresponding pre ferred and advantageous compounds of formula I. Particularly preferred is the compound 1 ,2,3,6-tetrahydrol-methyl-5-phenyl-5-( 2-pyridyl )-4( 5H )-pyrimidinone.

The pyrimidinones represented by formula III are useful as intermediates in the preparation of the corre sponding pyrimidinethiones of formula I by treatment of the compounds of formula lll with phosphorus pentasulfide in a solvent such as benzene. The pyrimidinones are prepared by condensation of an acetamide corresponding to a thioacetamide of formula ll with formaldehyde and ammonia or a primary amine as pre viously described.

The pharmaceutically acceptable, acid addition salts of the compounds of this invention are formed with organic and inorganic acids by methods known to the art. For example, the base is reacted with an organic or inorganic acid in an aqueous miscible solvent, such as acetone or ethanol, with isolation of the salt by concentration and cooling or in an aqueous immiscible solvent, such as ethyl ether or chloroform, with the desired salt separating directly. Exemplary of the salts which are included in this invention are maleate, fumaratc, succinate, oxalate, benzoate, methanesulfonate, ethanedisulfonate, benzene-sulfonate, acetate, propionate, tartrate, citrate, camphorsulfonate, hydrochloride, hydrobromide, sulfate, sulfamate, phosphate and nitrate salts.

The compounds of formula I are administered internally either parenterally, rectally or, preferably, orally in an amount to produce the desired biological activity.

Preferably, the compounds are administered in conventional dosage forms prepared by combining an appropriate dose of the compound with standard pharmaceutical carriers.

The pharmaceutical carrier may be for example a solid or a liquid. Exemplary of solid carriers are lactose, magnesium stearate, tcrra alba, sucrose, talc, stearic acid. gelatin, agar, pectin, acacia or cocoa butter. The amount of solid carrier will vary widely but preferably will be from about 25 mg. to about 1 gm. Exemplary of liquid carriers are syrup, peanut oil, olive oil, sesame oil, propylene glycol, polyethylene glycol (mol. wt. 200-400) and water. The carrier or diluent may include a time delay material well known to the art such as, for example, glyceryl monostearate or glyceryl distearate alone or with a wax.

A wide variety of pharmaceutical forms can be employed, for example the preparation may take the form of tablets, capsules, powders, suppositories, troches, lozenges, syrups, emulsions, sterile injectable liquids or liquid suspensions or solutions.

The pharmaceutical compositions are prepared by conventional techniques involving procedures such as mixing, granulating and compressing or dissolving the ingredients as appropriate to the desired preparation.

lt will be apparent to one skilled in the art that the compounds of this invention have an asymmetric carbon atom and thus optical isomers may be present. The

connotation of the formulas presented herein is to include all isomers, the separated forms as well as mixtures thereof.

The following examples are not limiting but are illustrative of the compounds of this invention and the processes for their preparation. Temperatures are in degrees Centigrade unless otherwise indicated.

EXAMPLE I A. To a mixture of 10.0 g. of 2-phenyl-2-( 2- pyridyl)thioacetamide and 4.5g. of methylamine hydrochloride in 200 ml. of methanol is added 7 ml. of

37% formaldehyde solution. The reaction mixture is stirred at 25 for l8 hours then the precipitated l,2,3.6- tetrahydrol -methyl-5-phenyl-5-( 2-pyridyl )-4( 5H pyrimidinethione hydrochloride is collected by filtration and recrystallized from ethanol, m.p. 264267. Treatment of a solution of the salt in water with 5% aqueous sodium carbonate until basic gives l,2,3,6 tetrahydrol methyl'5-phenyl-5-( 2-pyridyl )-4( 5H pyrimidinethione, m.p. 1 38 l 40.

B. A solution of 14.0 g. of Z-phenyl-Z-(Z-pyridyhacetamide in 200 ml. of methanol is treated with 6.75

g. of methyl amine hydrochloride and 4.0 g. of 37% formaldehyde solution. The reaction mixture is stirred for 12 hours at 25 then filtered to remove the product l ,2,3,6-tetrahydrol -methyl-5-phenyl-5-( Z-pyridyl 4(5H)-pyrimidinone hydrochloride, m.p. |70l73. Treatment of a solution of the salt in water with 571 aqueous sodium carbonate until basic gives l,2,3,6- tetrahydrol-methyl-5-phenyl-5-( Z-pyridyl )-4( 5 H pyrimidinone.

To a solution of l,2,3,6-tetrahydro l-methyl-5 phenyl-5-(Z-pyridyl)-4(5H)-pyrimidinone in benzene is added (H6 equivalent of phosphorus pentasulfide. The reaction mixture is heated gently for 30 minutes then water is added and the layers are separated. The aqueous layer is extracted again with benzene and the organic layers are combined, washed with water, dried (MgSO and concentrated in vacuo to give 1,2,13,6- tetrahydrol-mcthyl-S-phenyl-5-( Z-pyridyl )-4( 5H pyrimidinethione.

EXAMPLE 2 To a solution of 30 g. of 2phenyl2-(2- pyridyl )acetamide in 500 ml. of methanol is added 1 l .1 g. of ammonium chloride and ml. of 37% formaldehyde solution. The reaction mixture is brought to reflux and stirred for 12 hours. The mixture is then cooled and the methanol is removed in vacuo. Hot water (400 ml.) is added to the residue and the aqueous solution is made basic with 5% aqueous sodium carbonate. The resulting mixture is extracted with chloroform and the extract is washed with water and saturated sodium chloride solution, dried (MgSO and concentrated to give l ,2,3,6-tetrahydro-5-phenyl-5-( 2-pyridyl )-4( 5H pyrimidinone as an oil which crystallizes upon trituration with ethyl acetate, m.p. 20l203.

Treatment of l,2.3.6-tetrahydro-5-phenyI-5-(2- pyridyl)-4(5H)-pyrimidinone with phosphorus pentasulfide as described in the procedure of Example 1 gives l,2,3 ,6-tetrahydro-S-phenyl-5-( Z-pyridyl 4( 5H )-pyrimidinethione.

EXAMPLE 3 By the procedure of Example 1, using the following thioacetamides in place of 2-phenyl-2-( 2- pyridyl )thioacetamide:

2-phenyl-2-( Z-pyrazinyl )thioacctamide 2-( 4-chlorophenyl )-2-( 2-pyrimidinyl )thioacetamide 2-phenyl-2-( Z-thiazolyl )thioacetamide the final products are. respectively:

. l.2,3.6-tetrahydrol -methyl-5-phenyl-5-( 2- pyrazinyl )-4( 5H )-pyrimidinethione 5-(4-chlorophenyl)-1 2,3,6-tetrahydro-l-methyl-S- (2-pyrimidinyl )-4( 5H )-pyrimidinethione l ,2.3,6-tetrahydrol -methyl-5-phcnyl-5-( 2- thiazolyl )-4( 5H )-pyrimidinethione.

EXAMPLE 4 Substitution of the following 2-substituted phenyl-2- (Z-pyridyl )thioacetamides:

2-( 4-chlorophenyl )-2-( Z-pyridyl )thioacetamide 2-( Z-fluorophenyl )-2-( 2-pyridyl )thioaeetamide 2-( 4-methoxyphenyl )-2-( Z-pyridyl )thioacetamidc 2-( 3-methylphenyl )-2-( Z-pyridyl )thioacetamide in the procedure of Example 1 for 2-phenyl-2-( 2- pyridyl)thioacetamide gives the following compounds of this invention. respectively:

5-( 4-chlorophenyl l ,2,3.6-tetrahydrol -methyl-5- (2-pyridyl )-4( 5H )-pyrimidinethione 5-( 2-fluorophenyl l ,2,3,6-tetrahydrol -methyl-5- (Z-pyridyl )-4( 5H )-pyrimidinethione l,2,3,6-tetrahydro-5-( 4-methoxyphenyl 1 -methyl- 5-( Z-pyridyl )-4(5H )-pyrimidinethione l.2,3,6-tetrahydrol -methyl-5-( 3-methylphenyl )-5- (2-pyridyl )pyrimidinethione.

EXAMPLE 5 EXAMPLE 6 Methyl 4-thiazolyl ketone 12.7 g.) is added to 3.8 g. of sodium borohydride in I ml. of isopropanol and the mixture is heated at reflux for four hours. Dilute hydrochloric acid (100 ml.) is added and the mixture is evaporated to dryness. The residue is dissolved in a small volume of water and the aqueous solution is made basic with aqueous sodium bicarbonate solution, then evaporated to dryness. The residue is extracted with ether and the ether is removed from the extract in vacuo to give a-(4thiazolyl)-ethanol.

A mixture of 8.4 g. of oz-( 4-thiazolyl)ethanol and 25 ml. of thionyl chloride is heated for four hours on a steam bath, then concentrated in vacuo. The residue is dissolved in water and basified with 5% aqueous sodium carbonate solution. Extracting with ether, then drying and concentrating the extracts gives 4-(achloroethyl )thiazole.

A solution of 7.8 g. of 4-(a-chloroethyl)thiazole is added dropwise to a suspension of 5.2 g. of sodium cyanide in ml. of dimcthylsulfoxide. The mixture is heated at 50 for two hours, then diluted with I50 ml. of a 5% aqueous sodium carbonate solution and extracted with ether. The extract is dried and concentrated to give a-(4-thiazolyl)propionitrile.

To l2.4 g. of a-(4-thiazolyl)propionitrile in l3 ml. of pyridine is added 5 ml. of triethylamine. Hydrogen sultide is bubbled into the mixture for two hours. The mixture is heated in a sealed tube at l00 for 15 hours, then cooled and concentrated to dryness. The residue is extracted with chloroform and the extract is concentrated to dryness. The residue is recrystallized from chloroform-hexane to give 2-(4-thiazolyl)thiopropanamide.

Using 2-(4-thiazolyl)thiopropanamide in place of 2- phenyl-2-( 2-pyridyl)thioacetamide in the procedure of Example 1, the product is l,2,3,6-tetrahydro-l,5- dimethyl-5-(4-thiazolyl)-4(5H)-pyrimidinethione.

EXAMPLE 7 By substitution of an equivalent amount of methyl 4- pyrimidinyl ketone, methyl 2-pyrrolyl ketone or methyl 2-quinolyl ketone in the procedure of Example 6 for methyl 4-thiazolyl ketone followed by the subsequent synthetic steps described therein, there are prepared the following thiopropanamides:

2-( 4-pyrimidinyl )thiopropanamide 2-( 2-pyrrolyl )thiopropanamide 2-( Z-quinolyl )thiopropanamide. Substitution of a thiopropanamide listed above in the procedure of Example 1 for 2-phenyl-2-(2-pyridyl)- thioacetamide gives the following compounds of this invention, respectively:

1 ,2,3,6-tetrahydrol ,5-dimethyl-5-(4-pyrimidinyl 4( 5H )-pyrimidinethione l ,2,3,6-tetrahydro l ,5-dimethyl-5-( Z-pyrrolyl 4( 5H )-pyrimidinethione l,2,3,6-tetrahydrol ,5-dimethyl-5-(Z-quinolyl 4( 5H )-pyrimidinethione.

EXAMPLE 8 When ethylamine, isopropylamine, n-butylamine or t-butylamine or a corresponding hydrochloride salt is substituted in the procedure of Example l for methylamine hydrochloride, there are ultimately obtained the following pyrimidinethiones:

l-ethyl- 1 ,2,3,6-tetrahydro-5-phenyl-5-( 2-pyridyl 4( 5H )-pyrimidinethione l,2,3,6-tetrahydro-5-phenyll -isopropyl-5-( 2- pyridyl )-4( 5H )-Pyrimidinethione l-n-butyl-l ,2,3,6-tetrahydro-5-phenyl-5-( 2-pyridyl 4( 5H )-pyrimidinethione l-t-butyll ,2,3,6-tetrahydro-5-phenyl-5-( 2-pyridyl 4(5H)-pyrimidinethione.

EXAMPLE 9 2-Benzylpyridine (6.1 g.) dissolved in 25 ml. of dry benzene is added dropwise to 20 ml. of 2M phenyl lithium in benzene/ether with Cooling. The mixture is stirred for 30 minutes. then 2.6 g. of methyl isothiocyanate, dissolved in 40 ml. of dry benzene, is added dropwise with cooling. The resulting solution is stirred overnight. An equal volume of water is added and the solution is cooled and made acidic with 10% aqueous hydrochloric acid. The phases are separated. the organic phase is washed with water and the combined aqueous phases are made basic to about pH 9, then extracted with chloroform. The chloroform extracts are washed with water and dried over magnesium sulfate. Filtration and removal of solvent gives a residue which is recrystallized from isopropyl ether/ethanol to give N-methyl-2-phenyl-2-( 2-pyridyl )thioacetamidc.

Substitution of N-methyl-2-phenyl-2-(2-pyridyl)- thioacetamide in the procedure of Example I for 2- phenyl-2-( Z-pyridyl )thioacetamide gives 1,23,6- tetrahydrol ,3-dimcthyl--phenyl-5-( 2-pyridyl 4( 5H )-pyrimidinethione.

EXAMPLE Using, in the procedure of Example 9, the following isothiocyanatcs in place of methyl isothiocyanate:

ethyl isothiocyanate n-propyl isothiocyanate t-butyl isothiocyanate the following thioacetamides are obtained:

N-ethyl-2-phenyl-2-( 2-pyridyl )thioacetamide 2-phenyl-N-n-propyl-2-(2-pyridyl)thioacetamide N-t-butyl-2-phenyl-2-(2-pyridyl)thioacetamide. Reacting the above prepared thioacetamides with methylamine hydrochloride and formaldehyde by the procedure described in Example I gives the following products, respectively:

3-ethyl-l ,2,3,6-tetrahydrol -methyl-5-phenyl-5-( 2- pyridyl )-4( 5H )-pyrimidinethione l ,2,3 .o-tetrahydrol -methyl-5-phenyl-3-n-propyl-5- (Z-pyridyl )-4( 5H )-pyrimidinethione 3-t-butyll ,2.3,6-tetrahydrol -methyl-5-phenyl-5-( 2- pyridyl )-4( 5 H )-pyrimidinethione.

EXAMPLE I I When a thioacetamide listed in Example 10 is reacted with formaldchyde and ethylamine, isopropylamine, n-butylamine or t-butylamine, or a corresponding hydrochloride salt. according to the procedure of Example 1, there are obtained the following compounds of this invention, respectively:

I .3-diethyll .2.3,6-tetrahydro-5-phenyl-5-( 2- pyridyl )-4( 5H )-pyrimidinethione 3-ethyll .2,3,6-tetrahydro-5-phenyll-isopropyl-S- (2-pyridyl )-4( SH )-Pyrimidinethione I -n-butyl-3-ethyll ,2,3,6-tetrahydro-5-phenyl-5-( 2- pyridyl )-4( 5 H )-pyrimidinethione I-t-butyl-S-ethyll ,2,3 .fi-tetrahydro-S-phenyl-S-( 2- pyridyl )-4( 5H l-pyrimidinethione l-ethyll ,2 ,3,-tetrahydro-S-phenyl-I!-n-propyl-5-( 2- pyridyl )-4( 5H )-pyrimidinethione l ,2, 3,6-tetrahydro-5-phenyll -isopropyl-3-n-propyl 5 Z-pyridyl )'4( 5H )-pyrimidinethione l-n-butyll ,2,3,6-tetrahydro-5-phenyl-3-n-propyl-5- Z-pyridyl )-4( 5H )-pyrimidinethione l-t-butyl-l .2.3.o-tetrahydro-5-phenyl-3-n-propyl-5- Z-pyridyl )-4( 5H )-pyrimidinethione 3-t-butyll-cthyll ,2.3.6-tetrahydro-5-phenyl-5-( 2- pyridyl )-4( 5H )-pyrimidinethione 3-t-butyll 2.3.6-tetrahydro-S-phenyll -isopropyl-S- (2-pyridyl )-4( SH )-pyrimidinethione l-n-butyl-3-t-butyll .2,3,6tetrahydro-S-phenyl-5- (Z-pyridyl )-4( 5 H )-pyrimidincthione l,3-di-t-butyll .2,3.6-tetrahydro-S-phenyl-5-( 2- pyridyl )-4( SH )-pyrimidinethionc.

EXAMPLE I 2 To l g. of l,2,3,6-tctrahydro-l-methyl-S-phenyl-S- (Z-pyridyl)-4(5H)-pyrimidinethione in ether is added hydrogen bromide in ether to give the hydrobromide salt.

EXAMPLE l3 One gram of l,2,3,6-tetrahydro-l-methyl-S-phenyl- S-(Z-pyridyl)-4(5H)-pyrimidinethione in ethanol is treated with an equimolar amount of maleie acid in ethanol. The solvent is removed in vacuo to give the maleatc salt.

In like manner, using oxalic acid. the oxalate salt of l,2,3,6-tetrahydrol -methyl-S-phenyl-5-( 2-pyridyl 4( 5H )-pyrimidinethione is prepared.

Example 14 Ingredients Amount l 2 3.6-Tctrahydrol -methyl-5-phenyl- 5-( 'l-pyridyl )-4( 5H )-pyrimidinethionc 400 mg. Lactose I00 mg.

The above ingredients are mixed and filtered into a hard gelatin capsule.

In a similar manner, the other pyrimidinethione com pounds of this invention disclosed above may be formulated into capsules.

What is claimed is:

l. A compound of the formula:

pyrazinyl. 2-pyrrolyl, 2-quinolyl, Z-thiazolyl or 4- thiazolyl;

R is lower alkyl, phenyl or phenyl monosubstituted with halogen, lower alkyl of from one to four carbon atoms or lower alkoxy of from one to four carbon atoms; and

R and R are hydrogen or lower alkyl or a pharmaceutically acceptable acid addition salt thereof.

2. A compound according to claim 1 in which R is 2-pyridyl.

3. A compound according to claim 2 in which R; is

phenyl or phenyl monosubstituted with halogen, lower alkyl of from one to four carbon atoms or lower alkoxy of from one to four carbon atoms.

4. A compound according to claim 3 being the compound l ,2,3.6-tetrahydrol-methyl-S-phenyl-5-( 2- pyridyl )-4( 5H )-pyrimidinethione. 

1. A COMPOUND OF THE FORMULA:
 2. A compound according to claim 1 in which R1 is 2-pyridyl.
 3. A compound according to claim 2 in which R2 is phenyl or phenyl monosubstituted with halogen, lower alkyl of from one to four carbon atoms or lower alkoxy of from one to four carbon atoms.
 4. A compound according to claim 3 being the compound 1,2,3,6-tetrahydro-1-methyl-5-phenyl-5-(2-pyridyl)-4(5H)-pyrimidinethione. 